Ni修饰层对SnO_2薄膜气敏性能影响

Influence of Nickel Modification Layers on Gas Sensitivity of SnO_2-Based Gas Sensors

采用磁控溅射技术在SnO2薄膜表面修饰金属Ni，研究Ni修饰量对SnO2薄膜气敏性能影响。对Ni-SnO2薄膜进行表面成分分析，发现Ni的表面含量和化学价态对Ni-SnO2薄膜气敏性能影响至关重要。Ni的表面修饰量在3．4％-8．8％之间将有效提高SnO2薄膜对低浓度氢气的敏感性能。180℃工作温度下，表面含Ni3．4％的SnO2薄膜对1000ppm的氢气灵敏度最高为59．6，同时响应时间和恢复时间降低至15s和125s。Ni修饰量增加到23．4％，薄膜的气敏性能恶化，这是因为修饰层过厚，阻碍气体与SnO2材料接触。同时，XPS证实NiO是增加SnO2薄膜气敏性能的主要物质，增敏机理解释为Ni氧化后形成的NiO在SnO2薄膜上形成p-n结，促进元件的电导变化，从而提高了薄膜的气敏性能。

Small amount of nickel was deposited on SnO2 substrates by magnetron sputtering to improve the gas sensing property of SnO2- based sensors. The results show that nickel content in the surface modified layer and its stoichiometry significantly affect the gas sensitivity of the sensor. For instance, the surface with 3.4 % ～ 8.9 % of Ni considerably improves the sensitivity of low hydrogen concentration. At an elevated temperature of 180℃, the sensor, with a surface modified layer of 3.4 % nickel, shows a large H2 sensitivity, up to 59.6, in air with 1000 ppm hydrogen, but shorter response time （15 s） and recovering time（ 125 s）. However, when Ni concentration increases, up to 23.4%, the gas sensitivity considerably deteriorates possibly because Ni atoms reduce the density of gas absorption site. We propose that p-n junction formation, at the interface of p-type NiO and n-type-SnO2, changes the surface conductivity and improves the gas sensitivity.